increase sanity threshold for n_items per csa tag
DOC: add discussion of radiological / neurological

Also: clarify relationship of scanner-centric and subject-centric axis
arrangement.

Link to localizer image when mentioning same.
DOC: move neuro/radio discussion into own document

Maybe the discussion is a little specialized, so put it into a more
optional separate document.
adds tests for csareader.read nitems assertion
RF: slightly refactor csa tests; add test

Make error more explicit for too many items in the csa structure.

Add module global for max items and test
Merge pull request #1 from matthew-brett/refactor-csa-test

MRG: A little refactoring
Merge pull request #242 from kevlarkevin/increase_csa_nitems_assertion

MRG: increase sanity threshold for n_items per csa tag

Allow more items in csa tags.